package com.df.common.filter;

import com.df.common.utils.StringUtils;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * 防止XSS攻击的过滤器
 *
 * @author dunfeng
 */
public class XssFilter implements Filter {
  /** 排除链接 */
  public List<String> excludes = new ArrayList<>();

  /** xss过滤开关 */
  public boolean enabled = false;

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
    String tempExcludes = filterConfig.getInitParameter("excludes");
    String tempEnabled = filterConfig.getInitParameter("enabled");
    if (StringUtils.isNotEmpty(tempExcludes)) {
      String[] url = tempExcludes.split(",");
      for (int i = 0; url != null && i < url.length; i++) {
        excludes.add(url[i]);
      }
    }
    if (StringUtils.isNotEmpty(tempEnabled)) {
      enabled = Boolean.valueOf(tempEnabled);
    }
  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    HttpServletRequest req = (HttpServletRequest) request;
    HttpServletResponse resp = (HttpServletResponse) response;
    if (handleExcludeURL(req, resp)) {
      chain.doFilter(request, response);
      return;
    }
    XssHttpServletRequestWrapper xssRequest =
        new XssHttpServletRequestWrapper((HttpServletRequest) request);
    chain.doFilter(xssRequest, response);
  }

  private boolean handleExcludeURL(HttpServletRequest request, HttpServletResponse response) {
    if (!enabled) {
      return true;
    }
    if (excludes == null || excludes.isEmpty()) {
      return false;
    }
    String url = request.getServletPath();
    for (String pattern : excludes) {
      Pattern p = Pattern.compile("^" + pattern);
      Matcher m = p.matcher(url);
      if (m.find()) {
        return true;
      }
    }
    return false;
  }

  @Override
  public void destroy() {}
}
